Signaling system



April 15, 1941. c. E. LoMAx SIGNALING SYSTEM Filed April 21, 1939 3 Sheets-Sheet 2 INVENTOR. CLARENCE E LOMAX ATTORNEYS.

April 15, 1941. c. E. LoMAx SIGNALING SYSTEM Filed April 21, 1939 3 sheets-sheet 5 1NVENTOR. CLARENCE E LOMAX Rmb Qmk l www# SP@ L, f www QPF @n @vw Sw d 4 www@ 33TH* vr @Nm \N @Mw f @VQ b JNM. 2% p mg@ www @mi www @msm @n r 658 @nu @Sk WWE QFNJM H NGN@ Emi .www NM@ Sm Qbmv QRSMSQ QQ Sm SQ BYM-M-MM ATTORNEYS.

Patented Apr. 15, 1941 SIGNALING SYSTEM Clarence E. Lomax, Oak Park, Ill., assgnor to Associated Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application April 21, 1939, Serial No. 269,140

3 Claims.

The present invention relates to signaling systems and, more particularly, to series telegraph systems.

A fire alarm system conventionally comprises a dispatcher station, at which res are reported by box circuits or by telephone, a number of re stations, at which fire fighting apparatus is kept, and one or more series telegraph circuits extending between the various stations in order to facilitate the transmission of telegraphic messages therebetween.

An object of the present invention is to provide, in a telegraph system of the type noted, improved control apparatus at the various stations for facilitating the sending and the receiving of telegraphic messages in an easy and efcient manner.

Another object of the invention is to provide, in a telegraph system including a number of series telegraph circuits, improved switching apparatus at the various stations for controlling the connection of the sending and the receiving apparatus thereat to the various telegraph circuits and for controlling the completion of alternative telegraph circuits in the event the telegraph lines extending between adjacent ones of the stations are interrupted.

The features of the present invention are illustrated as being incorporated in a signaling system comprising a sending station, a plurality of receiving stations, position equipment being provided at each of the stations, a primary telegraph circuit including a source of current connecting the position equipment at the stations in series circuit relationship, and a secondary telegraph circuit including a source of current connecting the position equipment at the stations in series circuit relationship. The primary telegraph circuit includes a number of primary telegraph lines arranged in series circuit relationship and respectively extending between adjacent ones of the stations; and the secondary telegraph circuit includes a number of secondary telegraph lines arranged in series circuit relationship and respectively extending between adjacent ones of the stations.

In accordance with one feature of the invention, a manually operable sending device and an automatic sending device are provided at the sending station. Also, there is provided at the sending station manually operable switching means operative selectively to associate both of the sending devices with the primary and the secondary telegraph circuits and simultaneously to associate both of the sending devices with the primary and the secondary telegraph circuits. A receiving device is provided at each of the receiving stations; and a manually operable switch is provided at each of the receiving stations which is operative selectively to associate the receiving device thereat with the primary and the secondary telegraph circuits.

Also, there are provided'at the sending station first and second manually operable sending devices respectively normally connected in the rst and the second telegraph circuits, and rst and second manually operable switches. The rst manually operable switch at the sending station is operative to disconnect the rst sending device from the primary telegraph circuit and to connect the rst sending device in the second telegraph circuit; and the second manually operable switch is operative to disconnect the second sending device from the secondary telegraph circuit and to connect thesecond sending device in the primary telegraph circuit.

In accordance with another feature of the invention, the position equipment at each of the stations includes primary and secondary switching apparatus respectively associated with the primary and the secondary telegraph circuits, the primary switching apparatus included in the position equipment at adjacent ones of the stations being operable tovdisconnect the primary telegraph line extending between the adjacent stations from the primary telegraph circuit and to complete an alternative primary telegraph circuit including a ground return connection extending between the adjacent stations; and the secondary` switching apparatus included in the position equipment at adjacent ones of the stations being operable to disconnect the secondary telegraph line extending between the adjacent stations from the secondary telegraph circuit and to complete an alternative secondary telegraph circuit including a ground return connection extending between the adjacent stations.

Further features of the invention pertain to the particular arrangement of the circuit elements of the telegraph system, whereby the above-outlined and additional features are attained.

The novel features believed to be characteristic Aof the invention are set forth with particularity in the appended claims. The invention, both as to its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference lto circuit relationship by primary and secondary telegraph circuits respectively indicated at 50 and 60. Position equipment arranged at the stations |00, 200 and 300 are indicated respectively at |I0, 210 and 3|0. Also, the nre' station 200 comprises a number of batteries` 205,- 206v and 201, 200 for respectively supplying current to the primary and secondary telegraph lines 50 and 00, two battery chargers 203 and 200 for maintaining the batteries 205, 206 and 201, 200, respectively, in a charged condition, and a number of key switches K250, K255, K260 and K205 for controlling the connections of the batteries to the primary and secondary telegraph lines and to the battery chargers, in a manner more fully described hereinafter.

The position equipment at the dispatcher station |00 comprises a number of telegraph keys KIOI, K|02 and KI I1, an automatic sender |18, a printer P|02, a number of audible alarm devices AI01, A|09 and Al25, a number of supervisory lamps L||2, Ll23, Ll24, LI26, LI21 and LI28, a number of protective relays RI |3,

R|50, RI53, R100 and R|62, an impulse relay R|20, a test relay R|10, a number of thermostatic switches in the form of heat coils |12, |13, |14

and |15, a number of control keys K|01, K|00, f

KIII, KHG, KI30, KI36, KI40, KIM, KI56, Kl51, K105, KI66, KI61, KISS, K|82 and KI80. Preferably, the position equipment at each of the re stations, with the exception of the position equipment 2 I0 at the re station 200, is identical to the position equipment 3|0 at the nre station 300, which position equipment comprises a printer P335, two audible alarm devices A3|| and A352, and a number of control keys K3l3, K3IS, K321i, K330 and E335. The position equipment 2I0 at the fire station 200 is substantially identical to the position equipment 3 I0 at the re station 300 and includes, in addition thereto, two control keys K220 and X235.

The connection and arrangement of the signaling system and the position equipment at the yvarious stations will best be understood from a consideration of the description of the operation thereof appearing hereinafter.

The batteries 205, 200 may be selectively connected to the line conductors C210 and C21| of the primary telegraph circuit 50 and to the line conductors C2 II and C2|2 extending to the battery charger 203 by the key switches K250 and K255, respectively. For example, when the key switch K250 is operated away from its normal position in one direction, the positive terminal of the battery 205 is connected by way of the contact 25| thereof to the line conductor C210 of the primary telegraph circuit 50; and. the negative terminal of the battery 205 is connected by way of the contact 253 thereof to the line conductor C21| of the primary telegraph circuit 50. On the other hand, when the key switch H250 is operated in the other direction, the positive terminal of the battery 205 is connected by way of the contact 252 thereof to the line conductor C2i I extending to the battery charger 203; and the negative terminal of the battery 205 is connected by way of the contact 250 thereof to the line conductor C2|2 extending to the battery charger 203. In a similar manner, the batteries 201, 208 may be selectively connected to the line conductors C212 and C213 of the secondary telegraph circuit 60 and to the line conductors C230 and C28| extending to the battery charger 204 by the key switches K260 and K265, respectively.

.Assuming that the battery 205 is normally connected to the line conductors C210 and C21| of the primary telegraph circuit 50, a primary series circuit is normally completed including the position equipment ||0 at the dispatcher station |00 and-the position equipment at the several rire stations. Assuming that the battery 201 is normally connected to the line conductors C212 and C213 of the secondary telegraph circuit 60, a secondary series circuit is normally completed including the position equipment ||0 at the dispatcher station |00 and the position equipment at the several fire stations.

The primary series telegraph circuit 50 extends from the positive terminal of the battery 205 by way of the contact 25| of the key switch X250, C210, the contact 222 of the control switch K220, C202, the fuse |0|, the winding of the thermostatic switch |13, the resistor |58, the windings of the protective relays R|00 and R|62, the contact |88 of the key KISS, the contact |43 of the key KII0, CIQIS, RA|2|, the Winding of the alarm device AI01, the telegraph key KI 0|, the winding of the printing magnet PMIUB, C|95, the contact |33 of the key KI30, the contact |45 of the key KI40, C|9|, the contact |08 of the key KMS, the winding of the thermostatic switch |15, the fuse |02, C302, the position equipment at fire stations, not shown, the fuse 352, the contact 3|4 of the key K3I3, the winding of the alarm device A31 i, the contact 32| of the key K320, the winding of' the printing magnet PM341, the contact 324 of the key K320, C355, the contact 332 of the key K331i, the fuse 339, C350, the contact 232 of the key K230, C210, the Contact 221 of the key K225, 021| and the Contact 253 of the key switch K250 to the negative terminal of the battery 205.

The secondary series telegraph circuit 60 extends from the positive terminal of the battery 201 by way of the contact 26| of the key switch 200, C212, the contact 230 of the control key K235, C20I, the fuse |19', the Winding of the thermostatic switch |12, CI 98, the contact |38 of the key K|36, the contact |32 of the key KI30, Cl92, the winding of the protective relay R||3, the telegraph key K|02, the winding of the alarm device A|09, RAIZZ, CISS, the contact |35 of the key KI30, C|96, the contact |4| of the key KI40, Cl91, the contact |85 of the key KIBZ, the windings of the protective relays R|50 and R|53, the resistor |55, the Winding of the thermostatic switch |13, the fuse |80, CI, the position equipment at nre stations, not shown, the fuse 3110, the contact 331 of the key K335, the contactI 326 of the key K320, the winding of the alarm device A3l2, the contact 3|1 of the key K3|6, the fuse 353, CI, the contact 241 of the key K245, C215, the contact 2&2 of the key K240, C213 and the contact 263 of the key switch K260 to the negative terminal of the battery 201.

It is noted that the lightning arresters 303, 305 and 304, 306 are operatively associated with the primary and secondary telegraph circuits at the fire station 300, thereby to give the position equipment 3III thereat lightning protection. In a similar manner, the lightning arresters |18, |19 and |16, |11 are operatively associated with the primary and secondary telegraph circuits at the dispatcher station |00, thereby to give the position equipment |I thereat lightning protection. Similarly, lightning arresters, not shown, are operatively associated with the primary and Secondary telegraph circuits at the other lre stations, including the fire station 200, thereby to give the position equipment thereat lightning protection.

The fuses 330 and 352 in the re station 300, the fuses IOI and |82 in the dispatcher station |00, and similar fuses, not shown, in the other fire stations, including the fire station 2'00, are included in the primary telegraph circuit 50 in order to provide the primary telegraph circuit with ,s

mary and secondary telegraph circuits provide ff' these circuits with additional over current protection. It is noted that the adjustable resistors |58 and |55 respectively included in the primary and secondary telegraph circuits are provided for the purpose of regulating the normal flow of current from the batteries 205 and 201, respectively, therein.

The protective relays RI62 and R|50 respectively included in the primary and secondary telegraph circuits are oi the over-under current type. Speciiically, in the event the current in the primary telegraph circuit rises above a predetermined value, the relay RIB2 operates its armature to close the contact |63, thereby to complete an obvious circuit for illuminating the supervisory lamp LI28. Similarly, in the event the current in the secondary telegraph circuit rises above a predetermined value, the relay RI 50 operates its armature to close the contact I5 I thereby to complete an obvious circuit for illuminating the supervisory lamp LI21. On the other hand, in the event the current in the primary telegraph circuit falls below a predetermined value, the relay RIMI restores its armature to close the contact |64, thereby to complete the circuit for illuminating the supervisory lamp LI28. Similarly, in the event the current in the secondary telegraph circuit falls below a predetermined value, the relay RI50 restores its armature to close the contact I 52, thereby to complete the circuit for illuminating the supervisory lamp LI21. In the event that the primary telegraph circuit is interrupted, the protective relay RI60 restores to complete, at RAIII, an obvious multiple circuit for illuminating the supervisory lamp LI 2'4 and for operating the alarm device AI25. Similarly, in the event that the secondary telegraph circuit is interrupted, the protective relay RI 53 restores to complete, at RAI 54, an obvious multiple circuit for illuminating the supervisory lamp LI23 and for operating the alarm device AI25. The operation of the alarm device AI25 may be arrested by operating the keys K|51 or KI56, depending upon which of the previously mentioned operating circuits is completed, the completed circuit being indicated by the illumination oi the supervisory lamps LI24 and LI23. Also, in the event the seccondary telegraph circuit is interrupted, the protectiverelay RI I3 restores to complete, at RAI I5, an obvious path including the key KI I I for shortcircuiting the winding thereof and to complete, at RAI I4, an obvious circuit for illuminating the supervisory lamp LI I2. After the secondary telegraph circuit has been recompleted, the protective relay RI I3 may be reoperated by operating the key KI I I, thereby to interrupt the previously mentioned path for short-circuiting the Winding thereof. Upon operating, the protective relay RI I3 interrupts, at RAI I5, an additional point in the previously mentioned path for short-circuiting the Winding thereof and interrupts, at RAI I4, the previously mentioned circuit for illuminating the supervisory lamp LI I2.

In order to test the line conductors of the primary and secondary telegraph lines, in order to determine the presence of ground potential thereupon, an arrangement is provided which comprises the test relay RI10, the supervisory lamp LIZG, and the keys KIES, KI66, KI61 and KIB8, these keys being respectively associated with the line conductors C20I, C30I and C202,

C302, respectively, of the secondary and primary Y telegraph circuits 60 and 50. When one of these keys is operated, an obvious circuit is completed for energizing the .test relay RI10 in the event ground potential appears upon the corresponding line conductor of the telegraph circuit. Upon operating, the test relay RI 10 completes, at RAI'II, an obvious circuit for illuminating the supervisory lamp LI26, the illumination of the supervisory lamp LI26 indicating that the line conductor of the telegraph circuit corresponding 1go the operated key has ground potential there- It is noted that the operator at the dispatcher station |00 may transmit a message over the primary and secondary telegraph circuits selectively or simultaneously and that the message may be transmitted thereover either manually or automatically, as desired. A message may be manually transmitted over the primary telegraph circuit by operating the telegraph key 0I in an obvious manner. Each time the primary telegraph circuit is interrupted at the telegraph key KIUI, the winding of the alarm device AI01 is interrupted, thereby to cause the alarm device AI01 to operate and tap out ythe code of the message being transmitted. Similarly, each time the primary telegraph circuit is interrupted, the printing magnet PMI06 of the printer P|02 restores, thereby to cause the armature |04 thereof to print a record of the message being transmitted on the moving tape |05. In the event that it is undesirable to have the alarm device AI01 operate in accordance with the message being transmitted over the primary telegraph circuit, operation thereof may be arrested by operating the key KIO'I, thereby to complete an obvious path for short-circuiting the winding of ythe alarm device AI01.

A message may be manually transmitted over the secondary telegraph circuit by operating the telegraph key K|02 in an obvious manner. Each time the secondary telegraph circuit is interrupted at the telegraph key KI02, the Winding o-f .the alarm device AI09 is interrupted, thereby to cause the alarm device A|09 to operate and tap out the code ci the message being transmitted. The first time the secondary telegraph circuit is interrupted, the protective relay RI I3 restores, thereby to' complete the previously mentioned path for shortfcircuiting the winding thereof `and to complete the previously mentioned circuit for illuminating the supervisory lamp LI I2. The relay RI|3 remains in its restored position until the conclusion of the transmission of the message over the secondary telegraph circuit.

A message may be manually transmitted over the primary and secondary telegraph circuits si- A multaneously by operating ythe telegraph' key KI II in an obvious manner. Each time the telegraph key Kl Il is operated, an obvious circuit is completed for energizing the impulse relay RI20, thereby to cause the latter relay to operate, Upon operating, the impulse relay 'RIZD interrupts, at RAIEI, a point in the primary telegraph circuit and interrupts, at RAI22, arpoint in the secondary telegraph circuit. Also, a message may be automatically transmitted over the l primary and secondary telegraph circuits by initiating operation of Ithe sender II8, thereby to control the circuit for energizing the impulse relay Ri in an obvious manner.

As previously noted, the winding of the printing magnet PMEII'I in the fire station 300 is normally included in the primary telegraph circuit. Accordingly, each time the primary .telegraph circuit is interrupted, the printing magnet PMB'I restores, thereby to cause the armature 3130 thereof to print the message transmitted upon the moving tape 341. Also, it is noted that the winding of the printing magnet PM34'I may be excluded from the primary telegraph circuit and included in the secondary telegraph ciry.,

When the key cuit by operating the key K320. K320 is operated, an alternative path is completed between the conductors C302 and C350 in the primary telegraph circuit excluding the winding of the printing magnet PM34'I. This path extends from the conductor C302 by way of the fuse 352, the contact 3M of the key K3l3, the winding of the alarm device A3! I, the contact 323 of the key K322i), C355, the contact 332 of the key R330 and the fuse 339 to the conductor C350. Also, when the key K320 is operated, the Winding of the printing magnet PM34'I is included in the secondary telegraph circuit. The path for including the winding of the printing magnet Plvfll in the secondary telegraph circuit extends from the conductor C| by way of the fuse 340, the contact 331 oi the key K335, C358, the contact 322 of the key E320, the Winding of the printing magnet PMtli'I, the contact 325 of the key E020, the winding of the alarm device A3I2, the contact 3|? of the key KSIG and the fuse 353 to the conductor C35I. Thus, when the key H020 occupies its operated position, the printer P305 is operative to print the message transmitted over the secondary telegraph circuit. It will be understood that a printer is included in the position equipment 2|0 at the re station 200 and in the position equipment at the other nre stations and that keys correspondingto the key H320 are included in the position equipment at the several iire stations, thereby selectively to control the association of the printers included in the position equipment thereat with the primary and secondary telegraph circuits in the manner explained above.

An arrangement is incorporated in the position equipment at each of the several stations which is operative selectively to complete alternative primary and secondary telegraph circults by Way of a common ground return connection in the event aline conductor in the primary or secondary telegraph circuits extending between two of the stations is interrupted to cause the metallic primary or secondary telegraph loop circuits to be interrupted. For example, in the event the line conductor C302 included in the primary telegraph circuit and extending between the dispatcher station |00 and the fire station 300 is interrupted, neglecting for the present consideration the presence of the other re stations disposed between the dispatcher station |00 and the nre station 300, the metallic loop circuit of the primary telegraph circuit is interrupted in an obvious manner. In order to reestablish communication over the primary telegraph circuit, the key KI46 in the position equipment |I0 at the dispatcher station |00 is operated, thereby to interrupt, at the contact I 40 thereof, the connectionbetween the line conductors CI'9I and CI99 and to complete, at the contact |41 thereof, an obvious path for applying direct ground potential to the line conductor CI9I. Also, the key K3I3 in the position equipment 3I0 at the fire station 300 is operated, thereby to interrupt, at the contact 3M thereof, the connection between the winding of the alarm device A3II and the line conductor C302 and to complete, at the contact 3I5 thereof, an obvious path for applying direct ground potential to the winding of the alarm device A3I At this time an alternative primary telegraph circuit is completed including a ground return. This alternative circuit extends from a ground point by way of the contact SI5 of the keyv K3I3 in the position equipment 3| 0 at the re station 300 by way` of the previously traced circuit to the negative terminal of the battery 205, and from a ground point by way of the contact |47 of the key KI46 in the position equipment IIO at the dispatcher station |00 by way of the previously traced circuit to the positive terminal of the battery 205, the ground points mentioned being connected together by a suitable conductor, such, for example, as the city water distribution system.

Similarly, it will be understood that in the event the line conductor C202 included in the primary telegraph circuit and extending between the dispatcher station |00 and the fire station 200 is interrupted, an alternative primary telegraph circuit including a common ground return connection may be completed by operating the control key K220 in the position equipment 2I0 at the fire station 200 and the key KI86 in the position equipment IIO at the dispatcher station |00. In a similar manner, in the event the line conductor C350 included in the primary telegraph circuit and extending between the re stations 200 and 300 is interrupted, an alternative primary telegraph circuit including a common ground return connection may be completed by operating the key K230 in the position equipment 2I0 at the -iire station 200 and the key K330 in the position equipment 3I0 at there station 300. The alternative primary telegraph circuits completed incident to the operation of the keys in the position equipment at the several stations will be apparent fromv the foregoing example.

In a similar manner, it will be understood that alternative secondary telegraph circuits may be completed in the event the line conductors included in the secondary telegraph circuit and extending between the various stations are interrupted. For example, in the event the line conductor C30IA included in the secondary telegraph 'circuit and extending between the dispatcher station andthe fire station k30|), neglecting ffor the presentl consideration the presence of the other nre stations disposed between the dispatcher station U0 and the nre station 300, an alternative secondary telegraph circuit maybe completed by operating the keyiK|82in .the position equipment at the dispatcher station |00 and the key E335 in the position equipment 3|0 at the nrestation Stil. This alternative secondary telegraph circuit extends from a ground point at the contact |84 of the key K|82 by way of the previously traced circuit to the positive terminal of the battery 207, andv from 'a ground point at the contact 338 of the key K335 by way of the previously traced circuit to the negative terminal of the battery 251, the ground points mentioned being connected together by 'a suitable conductor.`

Similarly, it will be understood that in the event the line conductor CEM included in the secondary telegraph circuit and extending between the dispatcher station Iu and the fire station 205 is interrupted, an alternative secondary telegraph circuit may be completed by operating the key K|36 in the position equipment ||0 at the dispatcher station |00 and the control key K235 in the position equipment 2 Il] at the fire station Zilll. In a similar manner, in the event the line conductor 035| included in the secondary telegraph circuit and extending between the fire stations 200 and 3m] is interrupted, an alternative secondary telegraph circuit may be completed by oper ating the key K245 in the position equipment 2|0 at the re station 26D and the key K3|6 in the position equipment 3|() at the nre station 3230.

The alternative secondary telegraph circuits completed incident to the operation of the keys in the position apparatus at the lseveral stations Will be apparent from the foregoing example.

In the event the primary telegraph circuit 50 is completely interrupted due, for example, to the fact that both of the line conductors C202 and C352 included in the primary telegraph circuit and respectively extending between the dispatcher station |00 and the nre station 200 and the dispatcher station |90 and the fire,V station 300 are interrupted, it is` desirable to transfer the telegraph key Kllll and the printer P|02 normally included in the primary telegraph circuit into the secondary telegraph circuit. This may be accomplished by operating the key KIM) in the position equipment IIJ at the dispatcher station IUU. When the key K| is thus operated, the secondary telegraph circuit extends from the positive terminal of the battery 2|l`| by way of the previously traced circuit including the telegraph key Km2 to the conductor Ci, from the conductor CIBB by way of the contact |42 of the key KIM), CIM, RA|2I, the winding of the alarm device AIUI, the telegraph key KIDI, the winding of the printing magnet PMIDB, C|95, the contact |33 of the key K|30 and the contact |44 of the key KIM) to the conductor C|9'|, the conductor C|91 being connected by way of the previously traced circuit to the negative terminal of the battery 201. When the key KIM) isthus operated, further points in the primary telegraph circuit are interrupted at the contacts |43 and |45 of the key KMU. At this time the apparatus including the alarm 'device AI |11, the telegraph key K|U| and the printing magnet PMIDE, which is normally included in series circuit relationship with the primary telegraph circuit, is included in series circuit relationship with the secondary telegraph circuit.

In" the event the secondary telegraph circuit 60 is` completely interrupted due, for example, to the fact that both of the line conductors C2|| and C3| included in the secondary telegraph circuit and respectively extending between the dispatcher station |00 and the :tire station 23|] and the dispatcher station mi) and the nre station 3h0 are interrupted, it is desirable to transier 'the telegraph key Km2 normally included in the secondary telegraph circuit into the primary telegraph circuit. This may be accomplished by operating the key Kitt in the position equipment H0 at the dispatcher station HM). When the key KIM is thus operated, the primary telegraph circuit extends from the positive terminal of the battery 2&5 by way of the previously traced circuit including the telegraph key Kili! to the conductor Cls, from the conductor C|S5 by wayof the contact |t| of the key Klll, (H92, the winding of the protective relay BH3, the telegraph key Km2, the winding of the alarm device Alas, RAl22, the contact |34 of the key K|3|liand the/contact |155 of the key Kidd to the conductor Cisl, the conductor C|9| being connected by way of the previously traced circuit to the negative terminal oi the battery 205. When the key Kit@ is thus operated, further points in the secondary telegraph circuit are interrupted at the contacts |32 and `|35 of the key KIM. At this time the apparatus including the alarm device Atti), the winding of the protective relay RME and the telegraph key Km2, which is normally included in series circuit relationship with the secondary telegraph circuit, is included in series circuit relationship with the primary telegraph circuit.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

l. In a telegraph system, a sending station, a plurality of receiving stations, position equipment at each of said stations, a primary telegraph circuit including a source of current connecting the position equipment at said stations in series circuit relationship, said primary telegraph circuit including a number of primary telegraph lines arranged in series circuit relationship and respectively extending between adjacent ones of said stations, a secondary telegraph circuit including a source of current connecting the position equipment at said stations in series circuit relationship, said secondary telegraph circuit including a number of secondary telegraph lines arranged in series circuit relationship and respectively extending between adjacent ones of said stations, a common conductor extending between each two of said stations, the position equipment at adjacent ones of said stations being operable selectively to complete alternative primary and secondary telegraph circuits respectively exclud ing the primary and secondary telegraph lines extending between said adjacent stations and respectively including said common conductor extending between said adjacent stations, a sending device included in the position equipment at said sending station and adapted selectively to be operatively associated with said primary and said secondary telegraph circuits, and a receiving device included in the position 'equipment at each of said receiving stations and adapted selectively to be operatively associated with said primary and said secondary telegraph circuits.

2. In a telegraph system, a sending station, a plurality of receiving stations, position equipment at each of said stations, a primary telegraph circuit including a source of current connecting the position equipment at said stations in series circuit relationship, said primary telegraph circuit including a number of primary telegraph lines arranged in series circuit relationship and respectively extending between adjacent ones of said stations, a secondary itelegraph circuit including a source of current connecting the position equipment at -said stations in series circuit relationship, said secondary telegraph circuit including a number of secondary telegraph lines arranged in series circuit relationship and respectively extending between adjacent ones of said stations, a common conductor extending between each two of said stations, the posi-tion equipment at each of said sta-tions including primary and secondary switching apparatus respectively associated with said primary and said secondary telegraph circuits, the primary switching apparatus included in the position equipment at adjacent ones of said stations being operable to disconnect the primary telegraph line extending between said adjacent stations from said primary telegraph circuit and to complete an alternative primary telegraph circuit including Said common conductor extending between said adjacent stations, the secondary switching apparatus included in the position,

tobe operatively associated with said primary and said secondary telegraph circuits.

3. In a telegraph system, a sending station, a plurality of receiving stations, position equipment at each of said stations, a primary telegraph circuit including a source of current connecting the position equipment at said stations in series circuit relationship, said primary telegraph circuit including a number of primary telegraph lines arranged in series circuit relationship and respectively extending between adjacent ones of said stations, a secondary telegraph circuit including a source of current connecting the position equipment at said stations in series circuit relationship, said secondary telegraph circuit including a number of secondary telegraph lines arranged in series circuit relationship and respectively extending between adjacent ones of said stations, the position equipment at each of said stations including primary and secondary switching apparatus respectively associated with said 4primary and said secondary telegraph circuits, the primary switching apparatus included in the position equipment at adjacent ones of said stations being operable to disconnect the primary telegraph line extending between said adjacent stations from said primary telegraph circuit and to complete an alternative primary telegraph circuit including a ground return connection extending between said adjacent stations, the secondary switching apparatus included in the -position equipment at adjacent ones of said stations being operable to disconnect the secondary ltelegraph line extending between said adjacent stations from said secondary telegraph circuit and to complete an alternative secondary telegraph circuit including a ground return connection extending between said adjacent stations, a sending device included in the position equipment at said sending station and adapted Selectively to be operatively associated with said primary and said secondary telegraph circuits, and a receiving device included in the position equipment at each of said receiving stations and adapted selectively to be operatively associated with said prim-ary and said secondary telegraph circuits.

CLARENCE E. LOMAX. 

